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Chapter 8 File Contents |
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Not all systems support the classic tee program for splitting output pipes to multiple destinations. This command sends the output from someprog to /tmp/output and to the mail pipe beyond.
% someprog | tee /tmp/output | Mail -s 'check this' [email protected]
This program helps not only users who aren't on Unix systems and don't have a regular tee . It also helps those who are, because it offers features not found on other version of tee .
The four flag arguments are -i to ignore interrupts, -a to append to output files, -u for unbuffered output, and -n to omit copying the output on to standard out.
Because this program uses Perl's magic open, you can specify pipes as well as files.
% someprog | tctee f1 "|cat -n" f2 ">>f3"
That sends the output from someprog to the files f1 and f2 , appends it to f3 , sends a copy to the program cat -n , and also produces the stream on standard output.
The program in
Example 8.8
is one of many venerable Perl programs written nearly a decade ago that still runs perfectly well. If written from scratch now, we'd probably
use
strict
, warnings, and ten to thirty thousand lines of modules. But if it ain't broke . . .
#!/usr/bin/perl # tctee - clone that groks process tees # perl3 compatible, or better. while ($ARGV[0] =~ /^-(.+)/ && (shift, ($_ = $1), 1)) { next if /^$/; s/i// && (++$ignore_ints, redo); s/a// && (++$append, redo); s/u// && (++$unbuffer, redo); s/n// && (++$nostdout, redo); die "usage tee [-aiun] [filenames] ...\n"; } if ($ignore_ints) { for $sig ('INT', 'TERM', 'HUP', 'QUIT') { $SIG{$sig} = 'IGNORE'; } } $SIG{'PIPE'} = 'PLUMBER'; $mode = $append ? '>>' : '>'; $fh = 'FH000'; unless ($nostdout) { %fh = ('STDOUT', 'standard output'); # always go to stdout } $| = 1 if $unbuffer; for (@ARGV) { if (!open($fh, (/^[^>|]/ && $mode) . $_)) { warn "$0: cannot open $_: $!\n"; # like sun's; i prefer die $status++; next; } select((select($fh), $| = 1)[0]) if $unbuffer; $fh{$fh++} = $_; } while (<STDIN>) { for $fh (keys %fh) { print $fh $_; } } for $fh (keys %fh) { next if close($fh) || !defined $fh{$fh}; warn "$0: couldnt close $fh{$fh}: $!\n"; $status++; } exit $status; sub PLUMBER { warn "$0: pipe to \"$fh{$fh}\" broke!\n"; $status++; delete $fh{$fh}; }
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| 8.18. Program: tailwtmp |
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8.20. Program: laston |
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